Pneumatic nail-driving tools are old in the art and are exemplified by the devices disclosed in U.S. Pat. Nos. 3,498,517, 3,060,441, 3,035,268, 3,060,440, 3,595,460 and 3,711,008.
Prior hand-held pneumatic driving devices known to the art have not been suitable for heavy-duty fastener-driving operations, e.g., operations requiring installation of nails or fasteners to high strength substrates such as prestressed concrete having 5,000 to 10,000 psi compressive strength and structural steel plates with a thickness of 3/16th inch or greater. As a consequence, most heavy-duty fastener-driving operations are carried out with explosive-actuated devices which are time consuming and expensive and dangerous to operate. Furthermore, explosive-actuated fastener-driving means have substantial recoil and noise problems.
Prior attempts to provide pneumatic driving devices suitable for heavy-duty fastener-driving operations have been generally unsuccessful due to the difficulty of generating the required impact force to drive a nail or other fastener through high strength substrates such as concrete and steel plate. Because of the problems of generating the required acceleration, prior pneumatic driving devices designed for heavy-duty fastener-driving operations have been unduly complicated and have required complicated and large valving for feeding and exhausting the pneumatic fluid so as to generate the desired acceleration and impact force. Furthermore, most prior designs have involved a mechanical spring for assisting the driving member on its return stroke. However, the inclusion of spring means has had the undesired effect of limiting the acceleration of the driving member and the impact force exerted by such member on the fastener which is to be driven. Most hand-held prior art devices designed for pneumatically driving nails and similar fasteners have been low-energy devices, i.e., devices that provide for little or no acceleration time between the commencement of the work or driving stroke of the driving member and the impacting of the work by the fastener which is driven by the driving member. As a consequence, prior pneumatic driving devices have had to be massive in order to generate sufficient energy to accomplish heavy-duty fastener driving operations. Unfortunately, such prior driving devices also tend to have severe recoil.
The fastening device disclosed in related patent application Ser. No. 496,453 referred to above has the capability of driving fasteners, e.g., nails, into high resistant structural masses such as prestressed concrete with a compressive strength of 5000 to 8000 psi and structural steel plate with a thickness in the order of 1/4 inch -- a result that cannot be achieved satisfactorily with prior art pneumatic devices designed for fastener-driving operations.